The use of membrane technology in industrial processes is increasing; continuous processing, relatively mild conditions and appreciable reduction of energy consumption are the greatest advantages compared with conventional separation processes.
At present, polymeric (plastic) membranes, in particular, are used. However, these have the disadvantage of a low chemical and thermal stability, a low erosion resistance and an unduly low rigidity, as a result of which they can be compressed and the properties may vary.
Ceramic membranes offer a solution to this. The present generation of commercially obtainable ceramic membranes is still too expensive and has a low ratio of the membrane surface per unit volume. The method described in EP-B-0693961 deals with this. Use is made of a thermoplastic binder. As a result of a relatively simple processing, the cost price of the microfiltration hollow fibrous membranes is a factor of 3 to 10 lower than that of the present generation of ceramic membranes, while the surface/volume ratio, at more than 1000 m.sup.2 /m.sup.3, is up to 10 times higher. The abovemetioned method for making ceramic membrane fibres is eminently suitable for producing the fibres on an industrial scale.